The plan to extend Metrorail to Dulles International Airport has cleared another major hurdle.
The Office of Management and Budget was the final department within the Bush administration that needed to approve the first phase of the new line, which has been dubbed the "Silver Line."
That approval came Wednesday, nearly a year after officials threatened to strip the project of federal funding due to cost-efficiency concerns.
The Federal Transit Administration gave its approval last month.
The $5.2 billion project now goes before congress for a review that will likely take two months.
The Dulles Rail Project will be built in two phases; the first will run from Falls Church to Reston, passing through Tysons Corner. The second phase will run from Reston to Dulles, and onto Loudoun County.